1. Filed of the Invention
This invention relates to an image forming apparatus such as a copying machine, a facsimile apparatus or a printer, using an electrophotographic process.
2. Related Background Art
The basic construction of an image forming apparatus is shown in FIG. 8 of the accompanying drawings and the epitome of the operation thereof will hereinafter be described.
An electrostatic latent image bearing member 100 (hereinafter referred to as a photosensitive member) uniformly charged by a primary charger 101 is subjected to exposure 102 by image exposing means (not shown) for making image information into a latent image, whereafter the latent image is developed into a visualized image with toner by a developing unit 103.
A sheet P which is a recording medium is conveyed with its timing taken by registration rollers 104 and 105, and the toner image on the photosensitive member is electrostatically transferred to the sheet P by a transfer charger 106. Thereafter, the toner borne on the recording sheet is fixed by heat and pressure in a fixing unit 108 having a heating roller 109 containing a heat source therein and a pressure roller 110 urged against the heating roller.
Also, after the transfer, some developer untransferred and remaining on the photosensitive member 100 is scraped off by a cleaning unit 111 and is conveyed to a reservoir portion by a waste toner feeding member 112, and charges remaining as the latent image are eliminated by light of an eraser 113.
In the image forming apparatus as described above, various problems arise when the temperature in the apparatus becomes high.
The toner in the developing unit 103 is thermally deteriorated by heat generated from the fixing unit 108 and image density is reduced by a reduction in the charging potential or the waste toner in the cleaning unit 111 is coagulated by heat, and this leads to the trouble of the waste toner feeding member 112.
A fan 46 for exhausting the heat from the apparatus to suppress the temperature rise in the apparatus is disposed in the image forming apparatus so that these problems may not arise.
Also, near the exhaust fan, a filter 48 is disposed to prevent the developer and paper powder from being emitted from the interior of the apparatus.
However, by the long-term use of the apparatus, the toner and paper powder drifting in slight amounts in the apparatus and dust or the like in the air adhere to the filter and are accumulated thereon and as the result, they reduce heat exhausting efficiency and therefore, the inconveniences as previously described due to the temperature rise in the apparatus may be caused.
Against the above-noted problems, there have been proposed a method of detecting the temperature and humidity in the apparatus, and effecting the control of a rotating speed or a capacity of the fan, or effecting such control as changes the area of an opening portion through which heat is exhausted, and a method of installing a plurality of fans at a time and controlling the respective fans.
In the above-described methods, however, plural kinds of sensors and fans and a complicated control mechanism are necessary and the problems of increased cost, bulkiness and noise of the main body of the apparatus are unavoidable.
It is an object of the present invention to provide an image forming apparatus which has solved the above-noted problems peculiar to the conventional art.
It is another object of the present invention to provide an image forming apparatus which copes with even a temperature rise in the apparatus for a long period.
It is still another object of the present invention to provide an image forming apparatus which copes with even a temperature rise in the apparatus attributable to the clogging of a filter.
The present invention which achieves the above objects proposes an image forming apparatus for forming an electrostatic latent image on an electrophotographic photosensitive member, developing the electrostatic latent image and forming a developed image, and transferring the developed image to a recording medium to thereby form an image, wherein the image forming apparatus comprises: temperature detecting means for detecting temperature in the image forming apparatus; and control means for controlling a printing speed for forming the image so as to be reduced when the temperature detected by the temperature detecting means is a predetermined temperature T1 or higher.
Thereby, even when the filter is clogged by the long-term use thereof and heat exhausting efficiency is reduced, abnormal temperature rise in the apparatus can be prevented without spoiling the lower cost and downsizing of the main body of the apparatus and therefore, it becomes possible to obviate the creation of abnormal images and the trouble of the apparatus.